1. Field of the Invention
The present invention relates to a transmission control method and apparatus wherein, in transmitting data, a transmission line is occupied, and the data is sent toward unspecified receivers.
2. Description of the Prior Art
As discussed in, for example, IEEE CH 1796-2 (1982), p. 606-p. 614 in a prior-art apparatus transmission is controlled by a token, which is a code for granting the use of a transmission line. However, in communicating toward unspecified receivers, for example in broadcast communication, the receiver must receive all data items irrespective of whether or not they are necessary, and the case of the reception of unnecessary data is not desired is not considered.
With the prior art, a scheme for receiving data based on the judgement of the receiver is not taken into account, and unnecessary data is received. This has posed such a problem that the capacity of a device for storing received data must be enlarged, or the processing time of the receiver increases in correspondence with the reception of the unnecessary data.
Another problem of the prior art has been that the token, which is a code for granting the use of the transmission line, is handled as a special code, whereupon processing schemes must be changed according to the reception of the token or to the reception of the on-line data.